my car can inflate balloons :) ?

Hello,
i opened a topic about problem of coolant consumption,
now i would like to share with you this strange behaviour of my car

As i told, i am not able to find where my car leaks the coolant:
there are no spots on the floor, the motor is dry, and also the internal heat radiator is dry (i checked the carpets, they are dry).
So i did this:
I screwed the cap of the cooler tank,
and i put a plastic bag on the neck of the tank.

This is the result, let see this video:

https://youtu.be/LpNfHqudpNs

And this snapshot:
I did this try after the engine ran for some time,
i checked that this happens when the engine is hot, when the thermostatic valve is open.

You can see there is some water condensation in the bag.

What could be the cause of this behaviour?
It does not seem normal...

The obd scanner gives me fault p0402: EGR valve malfunctioning, but perhaps this is another problem

What do you think?


Thank you!

Hello,
any suggestion?

Thanks!

vicolodo wrote:Hello,
any suggestion?

Thanks!

If the system cap is leaking and not allowing the system to come up to pressure, you should replace it. Maybe is worn out or damaged. Have a look at this link to ebay to find a new replacement coolant cap for your C3.

Thank you, Arfur
Do you think the problem is the cap that is leaking,
or perhaps the cylinder head gasket is damaged?
Do you know how to check if the cylinder head gasket is damaged, and leaks pressure in the cooling circuit?
Thank you!

vicolodo wrote:Thank you, Arfur
Do you think the problem is the cap that is leaking,
or perhaps the cylinder head gasket is damaged?

Yes, could be either.

vicolodo wrote: Do you know how to check if the cylinder head gasket is damaged, and leaks pressure in the cooling circuit?
Thank you!

Well, the cheap option is to try a new cap and if the fault clears, it was the cap.

If you want to diagnose a head gasket, look for oil in the coolant or coolant in the oil or combustion gasses in the coolant using a head gasket tester kit.